Means for igniting and extinguishing furnace burners



3 Sheets-Sheet 1 OEZMAO wzmoaw MI INVENTOR. Fomey BY Fredrick Farney W62 ATTORNEYS R. H. FORNEY ETAL MEANS- FOR IGNITING AND EXTINGUISHING FURNACE BURNERS Dec. 3, 1957 Filed March 1, 1954 Dec. 3, 1957 R. H. FORNEY ETAL 2,815,068

MEANS FOR IGNITING AND EXTiNGUISHING FURNACE BURNERS Filed March "1, 1954 3 Sheets-Sheet 2 Fig.2

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MEANS FOR IGNITING, AND EXTINGUISHING FURNACE BURNERS Filed March 1, 1954 a sheets-sheet 5 MAIN T D L P GAS VALVE OPEN REGISTER GAS VALVE. CLOSED Fig.5

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A TTORNEYS United States Patent MEANS FOR IGNITIN G AND EXTINGUISHING FURNACE BURNERS Ross H. Forney and Fredrick E. Forney, Dallas, Tex. Application March 1, 1954, Serial No. 413,172 6 Claims. (Cl. 158-28) This invention relates to new and useful improvements in means for igniting and extinguishing furnace burners.

The invention is particularly concerned with means for automatically, and in a controlled sequence of steps, igniting or extinguishing fuel burners of the types employed in large installations such as steam boilers which may have a multiplicity of relatively large burners in each installation.

It has been the practice in large burner installations to ignite or extinguish such burners by manual operations at the burner location. This is true in spite of the existence of many types of automatic controls since no safe and certain procedure has been available which provides for the igniting of a furnace or boiler burner from a remote location wherein the operator is given positive assurance that the igniting or extinguishing operation is proceeding in the necessary and proper sequence.

It is, therefore, the principal object of this invention to provide improved means for igniting and extinguishing burners from a remote location.

It is a further object of the invention to provide means of the character described wherein the burner igniting or extinguishing operation is caused to proceed with indication at the remote location that the firing or extinguishing of the burner is proceeding properly in a correct and orderly fashion.

It is an additional object of the invention to provide an improved means of the character described having provision for automatically lighting the pilot burner associated with the main burner, to sense the proper ignition of the pilot burner, and to terminate the firing operation safely in the event proper ignition of the pilot burner does not occur.

An additional object of the invention is to provide an improved means of the character described having provision for ignition of the main burner following ignition of the pilot burner, and for sensing such proper main burned ignition to the extent of terminating the firing operation and closing the fuel and air admitting means in the event the main burner does not properly ignite.

A still further object of the invention is to provide an improved means for automatic remote ignition or extinguishing of furnace burners having provision for sensing the proper or improper operation of the means for admitting air and fuel to the burner, and for safely interrupting the firing operation in the event of malfunctioning with return of the burner elements to a safe or non-operating condition.

An additional object of the invention is to provide means of the character described with provision for manual ignition or extinguishing of the pilot burner at the location of the burner in addition to provision for remote control of this operation.

Still another object of the invention is to provide an improved means of the character described having provision for independent adjustment of the air admitting means subsequent to the firing operation.

Other and more specific objects and advantages of the invention will be apparent from a reading of the following description and specification and by reference to the accompanying drawing, wherein means for carrying out the invention are shown, and wherein:

Fig. 1 is a wiring diagram of a control apparatus constructed in accordance with this invention and adapted to carry out the steps herein disclosed,

Fig. 2 is a front elevation of a burner unit having incorporated therein a control system as contemplated by this invention,

Fig. 3 is an enlarged view in elevation of the interlock switches for the air register and fuel valves,

Fig. 4 is an enlarged view in elevation of the limit switches for the valve and register operators,

Fig. 5 is a View of the face of the central station control unit,

Fig. 6 is a view of the face unit, and

Fig. 7 is a schematic wiring diagram of the interlock switch structure.

It has become conventional to employ large furnaces or boilers, each of which may contain a considerable number of burners for gas or oil combustion. In such installation, and in particular, in the larger steam boilers, the burners sometimes require very rapid ignition or extinguishing in order to match the output of the boiler to the existing power load or demand. It is quite apparent that the usual practice of extinguishing or igniting burners manually at the burner location becomes a time consuming process in the case of a boiler having possibly as many as 24 burners arranged in superposed banks which may be 6 to 8 feet apart. Since only one or two attendants are often available for this operation, the mere physical movement of the attendant from one burner to the next and from one bank of burners to the next lower or next above bank consumes a certain amount of time so that the attaining of the desired firing or extinguishing of burners within the space of a minute or two is not humanly possible. The present invention solves this problem by providing a simple control actuating arrangement, one of which may be located in a central control room for each of the burners of a furnace, and provides for operation and control of a number of furnaces, each of which may have a multiplicity of burners. Upon actuation of the centrally located unit, there is placed in operation an electrical control unit which admits a combustible fuel mixture to the pilot burner of the particular furnace burner being operated, ignites this fuel mixture and senses the proper establishment of a pilot flame, which opens the fuel and air admitting means for the main burner in order that they may be ignited by the pilot flame and senses the proper establishment of the main burner flame, which provides for the full opening of both the fuel and combustion air-admitting means, which terminates the burner igniting operation if all con ditions requisite to proper burner operation are not promptly established, and which, in terminating the ignition operation, closes off the fuel and air supplies and places itself in a condition wherein recycling of the ignition sequence does not occur prior to positive manual manipulation of the switch structure provided in the central control room.

In Fig. l of the drawings there is shown the wiring diagram of a control unit adapted to carry out the teachings of this invention and in which are included a number of electrically operated relays, each of which is adapted to open or close one or more pairs of contact points. For clarity of explanation, the normal con dition of each of these relays will be considered to be that condition of the relay when no electric current is of the local station control flowing in the coil thereof, or when the relay is not energized. Those pairs of contact points which are not in engagement when the relay is not energized will be termed normally-open contacts, while those pairs of contact points which are in engagement to close a circuit when the relay is not energized will be termed normallyclosed contacts. Of course, when a relay is energized by activation of its coil, its normally open contacts are caused to engage and close a circuit while its normally closed contacts are caused to separate and open and hence, to interrupt the circuit. Further, each relay will be identified by a numeral which is an even multiple of ten and by the aflixing of that numeral to the energizing coil of that relay in the drawings. The contact points of any particular relay will be identified by the number of that relay plus a small whole number.

Referring now to Fig. 1 of the drawings, the numeral 5 designates a single-pole switch adapted to supply electric current, such as 110 volts A. C. to any one of three terminals. Desirably, the switch may be manually operated and is located in the central control room of a power plant or other installation in which large furnaces or boilers are employed. The burner-igniting terminal 6 of the switch 5 is connected to a hot lead or wire '7 to which are connected in parallel certain of the contact points of a firing relay Ill and a holding relay 20. One side of the coil of relay 10 is grounded, and the hot side of the coil is connected through normally-closed contacts 21 of the relay 2% to the hot lead '7. Similarly, one side of the relay Ztb is grounded, and the hot side of the coil is connected in parallel through normally-open contacts 22 of the relay 26 to the hot lead 7. Normally-open contacts 23 of the relay 2) and normally-closed contacts 12 of the relay 10 are connected in series between the hot lead 7 and the burner extinguishing terminal 3 f the switch 5. There are also normally-open contacts 13 of the relay 10 connected between the hot lead 7 and one side of the coil of a time delay relay 4d. The time delay relay has the other end of its coil grounded and is provided with normally-closed contacts 41 also connected to the lead 7 through the contacts 13.

A burner extinguishing terminal 8 is arranged to be energized through the switch 5, as well as through the contacts 12 and 23, and is connected to one end of the coil of a burner extinguishing relay 56). The opposite end of the coil is grounded, and the burner extinguishing relay is provided with two normally-open contacts 51 and 52 connected between the terminal 8 and the actuating mechanism for closing the air and fuel inlets to the furnace burner. As will be described more fully hereinafter, the control of admission of fuel and air to the main burner may be achieved through the use of lever-operating motors or some other suitable means, which, in turn, may be operated through motor controllers, motor-operating relays, or other conventional actuating equipment not herein illustrated. The contacts 52 of the relay 50 are connected between the terminal 8 and an electrical conductor 52 leading to the operating mechanism, or the operating control mechanism, for closing the fuel valve to the main burner. The contacts 51 of the relay are similarly connected between the terminal 8 and an electrical conductor 51 leading to the mechanism or structure for closing the air admission means to the main burner.

The relay is also provided with normally-open contacts 1 connected between the hot lead 7 and one end of the coil of a burner firing relay 60. The opposite end of the coil of the relay 60 is grounded, and the relay is provided with a pair of normally-open contacts 61 and 62. The contacts 62 are connected between the hot end of the coil of the relay 60 and an electrical conductor 62' leading to conventional mechanism for opening the fuel supplying means for the main burner, while the contacts 61 are connected between the hot end of the coil of the relay 60 and an electrical conductor 61' leading to the structure for admitting combustion air to the main burner. The air register closing and opening leads from the contacts 51 and 61 are also connected to the terminals of a single-pole double-throw switch 63 having its switch arm connected to the third terminal 64 of the switch 5. Thus, when the switch 5 is positioned to supply power to the terminal 64, the switch 63 is potentialized and may be operated manually to supply power to either of the air register power leads and open or close the register manually as desired. A grounded electrical conductor 64 is provided and extends to both the air register opening and closing means and the fuel supply opening and closing means for completing an electrical circuit thereto.

There is provided in conjunction with the pilot burner a pilot control unit 65 having therein a power supply transformer 66 fed from 110 volt A. C. leads 67. The neutral lead 67 is grounded and the hot lead 67 is connected through normally-open contacts 68 of the relay 60 to the hot end of the coil of a relay 70. The opposite end of the coil is grounded. Normally-open contacts 71, adapted to be closed by actuation of the relay 70, are connected between the hot lead 67 and the automatic terminal 72 of a manual pilot lighting switch unit 73.

Any suitable means may be employed for sensing the presence of a pilot flame, but it is preferred to use an electrode detector of the type which functions due to conductivity between a pair of electrodes exposed to the ionized gases present in the pilot flame. For this purpose, there is provided a grounding electrode 74 so positioned as to be within the pilot gas flame, and connected to the pilot gas burner 75 as well as to one input lead of an electronic conductivity sensing unit 76. The second electrode 77, is also positioned to be within the pilot gas flame and is connected through the normallyopen contacts 78 of the relay 70 to the other input lead of the unit 76.

The unit 76 is powered through the transformer 66 and is of conventional structure and arrangement for the purpose of sensing conductivity between electrodes 74 and 77 and amplifying the signal thus received in order to energize the coil of a pilot flame relay 30. Such structures are well known and are commercially available so that no further description thereof is thought necessary or essential.

The manual ignition unit 73 carries a single-pole double-throw switch 82 having its switch bar normally engaging between a transformer lead 83 and a terminal 84. The switch is of the momentary break type, and upon breaking of the circuit between the lead 83 and the terminal 84, closes a circuit between the lead 83 and a terminal 85 to which 110 volt alternating current is supplied.

The terminal 84 of the switch 82 is connected through normally-closed contacts 86 of the relay 80 to the contacts 71 of the relay 70. The relay 80 also has normallyopen contacts 87 connected between the con-tacts 71 and the coil of a relay 90. The opposite end of the coil of the relay 90 is grounded.

The relay 90 is provided with normally-open contacts 91 connected in parallel with an interlock switch 92 from the hot end of the coil of the relay 10 through a pair of interlock switches 93 and 94, arranged in series, to the contacts 4-1 of the relay 4-0. The interlock switches 92, 93 and 94 will be described in further detail hereinafter, it being noted at this point that switches 92 and 93 are cam-operated switches actuated by opening and closing of the fuel and air admitting means for the main burner. The switch 92 is closed when the fuel and air admitting means are closed or nearly closed, and is adapted to open as these means open. The interlock switch 93 is opened when the air and fuel admitting means are fully open, but is closed prior to the substantially full opening of said means. The switch 94 is a pressure-actuated switch having its pressure-responsive means exposed to the fuel supply line leading to the main burner and responsive to the pressure therein downstream of the fuel admission control means. The switch 94 is normally-closed and is arranged to open when a predetermined pressure is reached in the fuel supply conductor leading from the fuel admission controlling means or valve to the main burner.

There is also provided an interlock switch 98 in a shunt across the contacts 41 of the relay 40, this latter interlock switch being open prior to opening of the fuel and air admitting means, and closing when said means reach their fully open position.

The system is also provided with a main burner flame sensing unit 99 having therein a main burner flame relay 100 adapted, upon energization, to close normally-open contacts 101 connected in a shunt across the switches 93 and 94. The control unit 99 is provided with power supply leads 102 connected to the primary of a transformer 103. The neutral lead 102 is grounded, and the hot lead 102 is connected through normally-open contacts 104 of the relay 100 to a signal lamp 105 located in the central control room adjacent the switch 5.

The transformer 103 feeds an electronic flame sensing unit 106, which may be any suitable or desirable variety of these commercially available units for amplifying a signal and actuating a relay coil or other instrumentality. The sensing leads of the unit 106 are connected to a photocell 107, and upon the reception of an adequate signal from the photocell 107, the unit 106 energizes the coil of the relay 100.

The photocell 107 is of the commercially available type having maximum sensitivity to blue light and little sensitivity to red light. The cell is positioned to receive direct light from the main burner flame, and there is interposed between the cell and the flame a condensing lens 103. Having a somewhat larger area than the cell 107, the lens 100 gathers light from the main burner flame over a considerably larger area, and concentrates this gathered light upon the photocell which is positioned at or near the point at which light rays from the main burner flame converge or are concentrated by the lens 108. In this manner, the relatively weak emanation of short wave-length light from a gas flame may be concentrated and amplified to a level adequate to cause the photocell 107 to function. An oil flame normally produces adequate light of this nature so that the lens may not be required.

In order to permit automatic lighting of the pilot burner, the local control unit 73 is provided with a singlepole double-throw switch 109 having as one terminal the terminal 72. The other terminal 110 of the switch is supplied with electrical power such as 110 volts A. C. The switch bar of the switch 109 is connected to ground through a signal light 111 within the unit 73, through a signal light 112 located at the central control station adjacent the switch 5, and through the coil 113 of a solenoid valve 114 interposed in the fuel supply conductor 115 leading to the signal gas burner 75. The pilot lights 111 and 112 and the coil of the solenoid valve 114 are all arranged in parallel between the switch 109 and ground, and hence are energized simultaneously whenever the switch bar is swung into engagement with the terminal 110, or whenever power is supplied to the terminal 72 through the contacts 71 of the relay 70.

In the operation of this control unit, it may be assumed that the fuel supply valves for the pilot burner and the main burner, as well as the air register for the main burner are all in closed position. Hence, the pilot fuel valve 114 will be closed, the interlock switches 92 and 93 are closed, and the interlock switch 98 is open. Because there will be no pressure in the fuel supply conductor to the main burner because of the closed condition of the fuel supply valve, the pressure relay switch 94 will also be closed.

When it is desired to ignite the burner, the switch 5 is moved into engagement with terminal 6 thus supplying power to the hot lead or wire 7. This energizes the relay 10 through the contacts 21, actuating relay 10 and closing contacts 11 and 13.

The relay 40 is of the time-delay type which functions a predetermined period of time after energization. In one particular embodiment of the present invention, it has been found that approximately 7 /2 seconds are required to open the fuel valve and the air register to the main burner, and it has been found advantageous to set the relay 40 to operate after a fifteen second delay. Prior to such operation, however, the contacts 41 thereof are closed and a circuit is thus completed from the contacts 13 through the contacts 41, the switches 93 and 94, and the switch 92, to the coil of the relay 10. A secondary circuit for holding the relay 10 energized is thus provided.

The energization of the relay 10 also closes the con tacts 11 which energizes the coil of the relay 20, closing the contacts 22 and 23, and opening the contacts 21. The closing of the contacts 22 causes the relay 20 to function as a self-holding relay, and the relay will not again open until the switch 5 is disengaged from the terminal 6. At the time the relay 10 is energized, the normally-closed contacts 12 thereof are opened, and hence, the closing of the contacts 23 does not complete a circuit to the coil of the relay 50 whereby the actuating leads to the air register and fuel valve closing means are not energized. The opening of the contacts 21 would deenergize the relay 10 except for the establishment of the alternate circuit described above. It is further noted that energizing of the relay 10 closes the contacts 14 thus energizing the coil of the relay 60 and closing the contacts 61 and 62 thereof to commence the opening of the air register and fuel valve.

The actuation of the relay 60 also closes the contacts 68 and thereby energizes the coil of the relay 70 in the pilot burner igniting unit 65. Relay 70 closes the normally-open contacts 78, thus connecting the electrodes '74 and 77 to the unit 76 whereby the presence of a pilot flame may be sensed, and also closes contacts 71 supplying energy to the terminal 72, and, through the normally-closed contacts 86 of the relay 80 to the switch terminal 04.

The switch 109 of the local or manual pilot burner igniting unit 73 normally remains in its automatic position in engagement with the terminal '72, and hence, the supplying of electrical energy to this terminal lights the signal lights 111 and 112 and opens the solenoid valve 114. The illumination of the light 112 at the central control station informs the attendant that the pilot unit has commenced operation.

The supplying of electrical energy to the terminal 04 of the unit 73 causes energy to flow through the switch 02 to the lead 03 and the primary winding of a high voltage transformer 116. The secondary of the transformer is connected to a spark gap 11'? positioned closely adjacent the pilot burner 75?, and the spark thus produced ignites the fuel flowing from the pilot burner. As soon as the pilot flame is established, conductive conditions between the electrodes 74 and 77 are established, and the signal thus provided to the unit 76 causes the latter to energize the coil of the relay 80 thus closing contacts 8'7 and opening contacts 86. The opening of contacts 06 de-energizes the transformer 116, while permitting power to continue to flow through the contacts 71 to the solenoid valve 114 and the signal lights 11.1 and 112. The closing of the contacts 07 delivers electrical energy from the contacts 71 to the coil of the relay 90, thus closing the contacts 91 of the latter relay and establishing that portion of the circuit to the coil of the relay 10. The opening of the interlock switch 92 due to the commencing of the opening of the fuel valve and the air register is delayed a sufficient time in order to permit these operations to take place since only a second or so is required or closing of the contacts 91 it normal ignition of the pilot flame is achieved. Of course, if the pilot burner does not ignite, the relay 30 is not energized, and there is no energization of the relay 9@ or closing of the contacts 91. In this case, after the few seconds required for opening of the switch 92, the circuit to the coil of the relay 10 would be broken and the igniting operation would be terminated. Further, at any time the pilot burner flame is extinguished or there is failure to maintain a pilot flame of the adequacy previously selected as suflicient to create conductivity between the electrodes '74 and 77 and to deliver to the unit 74: a signal of sufficient strength, then the relay 8i) is de-energized resulting in opening of the contacts 91 and de-energization of the relay It).

When the pilot flame is established and such condition has automatically been responded to by the control system, the fuel valve and air register will have been opened sufliciently as to institute the main burner flame which, of course, is ignited from the pilot flame. Upon ignition of the main burner, the blue light from the flame thereof will be gathered by the lens 108 and concentrated upon the photocell 197 thus delivering a signal to the unit 106 resulting in energization of the coil of the relay 1% and closing of the contacts 191 and 104. Closing the contacts 101 provides a shunt circuit around the switches 93 and 94 and thus maintains the alternate circuit to the relay it). The closing of the contacts 104 ignites the pilot light 1% and informs the attendant that an adequate main burner flame has been established. The fuel pressure in the supply conductor to the main burner will not rise instantaneously since a small period of time is required for opening of the fuel valve. Further, the switch 94 may be adjusted to open at any desired pressure level, or may even have some slight time delaying structure incorporated therein. The second or so required for the switch 94 to open is sufficient for establishment of the main burner flame and adequate to hold the circuit to the coil of the relay 10 closed until the relay 1% is energized. The delay in opening of the switch 93 due to the fact that a number of seconds are required for the air register and fuel valve to reach fully open position is also instrumental in maintaining this circuit prior to actuation of the relay 1%.

The switch 93 is incorporated in series with the switch 94 since the pressure of the fuel supply may not reach a level suflicicnt to open the switch 94 and since the system may thus be deprived of the protection of the unit 99. in the event the fuel pressure never reaches a level SllffiClEJIli to open the switch 94, the switch 93 will nevertheless be opened when the air register and fuel valve reach their open position, and hence, the attendant is assured that the continued operation of the control system is being effected through proper energization of the relay 1%. In the absence of such energization, the opening of the switch 93 will terminate the igniting operation.

The provision that the time delay relay operates after a predetermined and relatively short interval makes certain the openings of the contacts 41 after such interval. The switch 98 does not close until the air register and fuel valve are fully open. Hence, unless the fuel and air control means have opened fully at the end of the time period for which the relay Ml has been adjusted, the holding circuit to the relay 10 is opened and the relay is de-energized. From the foregoing, it is apparent that the system makes provision for protection against a considerable number of malfunctionings, and it is prerequisite to the continued operation of the system that the pilot flame be established and remain of suflicient magnitude, that the main burner flame be established and remain of suflicient intensity as to result in actuation of the relay 190, and that the air register and fuel valves open fully. The failure to achieve or retain any of these conditions during the igniting operation or subsequently thereto results in de-energization of the relay 10 which immediately opens the contacts 14, de-energizing the relay 60 and stopping the opening action of the air register and fuel valve control means actuated by the latter relay. Further, the contacts 11 and 13 are opened, placing the relay 20 entirely on the self-holding circuit through the contacts 22, and positively breaking beyond re-establishment the alternate circuit to the coil of the relay 10. The continued energization of the relay 20 holds the contacts 21 open placing full control of the relay 10 on the contacts 13, and holds the contacts 23 closed. The de-energization of the relay 10 results in closing of the contacts 12 and the establishment of a circuit to the coil of the relay 50, closing the contacts 51 and 52 and thus immediately energizing the means for closing the air register and fuel valve. Thus, in the event any difliculty is encountered in the burner lighting operation or in the event any malfunctioning occurs, the opening of the fuel valve and the air register is immediately stopped, and closing of the register and valve is initiated. The system is locked in this non-functioning condition so long as the switch 5 remains in engagement with the terminal 6. A circuit to the coil of the relay 10 cannot be established because both the contacts 13 and 21 are open, and regardless of what takes place elsewhere in the system, the relay 22 remains energized with the relay lit deenergized. The circuit to the register and valve opening relay 60 is held open in a positive fashion by the opening of the contacts 14, and the circuit to the register and valve closing relay 50 is maintained closed. Of course, both on opening and closing of the air register and the fuel valve, suitable limit switches are provided in the usual and conventional fashion for shutting off operation of the opening and closing means after the register and the valve reach a fully open or a fully closed position.

After proper lighting of the burner has been effected, the switch 5 is normally returned into engagement with the terminal 64 in order to remove the various sensing and control elements from the circuit and to prevent nuisance shutdowns of the burner due to a possible malfunctioning of the control equipment. In this position of the switch 5, the switch 63 is potentialized, and may be moved manually into engagement with either of its contacts or terminals in order to energize the electric conductors leading to the means for opening and closing the air register. The position of the air register may thus be closely adjusted manually following automatic ignition of the main burner.

It is also important that the rapid extinguishing or shutting down of a burner be made possible, and this is achieved by simple manual movement of the switch 5 into engagement with the terminal 8. This action directly energizes the coil of the relay 50, closing the contacts 51 and 52 and closing the air register and fuel valve within a matter of seconds. No control operations or safety precautions are required at this point, and the balance of the system does not function at this point.

It is further to be noted that manual lighting of the pilot burner at the control unit 73, which normally is in the proximity of the burner structure may readily be carried out. In this local operation of the pilot burner, the switch 109 is manually moved from engagement with the terminal 72 to the'terrninal 110 which energizes the signal lights 1 11 and 112, and opens the solenoid valve 114. The momentary contact switch 82 is then depressed into engagement with the terminal 85, thus energizing the transformer 116 and the spark mechanism 117. Effective ignition of the pilot burner is thus obtained, and the pilot flame igniting unit 65 become effective even though the switch 109 is not returned into engagement with the terminal 72. As usual and customary in such installations, manually operable switches may be provided locally at the site of the burner in order to operate the air register and fuel valve opening and closing means, and hence, air and fuel may be admitted to the main burner at the location of the burner.

' It is noted that the control means provides a considerable number of safety features both before, during, and after ignition of the main burner, so long as the switch remains in engagement with the terminal 6. Prior to institution of the lighting cycle, the fuel valve and air register must be closed since otherwise the switch 92 is open and the holding circuit of the coil of the relay will be broken as soon as the relay 20 is energized and the contacts 21 are opened. As soon, however, as the air register and fuel valve reach the point in their opening movement at which the switch 92 is opened, contacts 91 must be closed through proper lighting of the pilot burner, or otherwise, the holding circuit to the relay 10 will again be broken. As the fuel pressure acting upon the switch 94 increases, the switch is opened, and hence, proper ignition of the main burner flame must be instituted. Thus, unless proper and almost instantaneous ignition of the main burner flame occurs, the relay 10 is de-energized by opening of the switch 94 and the system is locked into an air register and fuel valve closing condition.

Assuming the main #burner to be properly lighted, then full opening of the air register and fuel valve must be completed Within the time of operation of the time delay relay 40 in order to close the switch 98. Otherwise, upon the opening of the contacts 41, relay 10 will be de-energized and the i nition operation will be stopped and reversed.

Of course, if there is no fuel supply to either the pilot burner or the main burner, or if the fuel supply is inadequate, proper ignition will not occur and the system will lock itself out of operation. Of course, this safeguard continues so long as the system is operative and will result in closing of the air register and fuel valve if fuel or flame failure occurs at any time.

Since the energization of the relays 80 and 100 are essential to continued functioning of the control system, and since the proper function of these relays is in turn dependent upon the units 76 and 106, along with their transformers 66 and 193 and the power supplies 67 and 102, any failure in any of these elements or in any of their component parts will result in an opening of the circuit to the relay 10 with consequent closing of the air register and fuel valve. Normally, however, this is of importance only during the lighting operation and for a short period thereafter until the switch 5 is moved from engagement with the terminal 6. Usually, it is not desirable to hinge the continued operation of the main burner upon this control system due to the possibility of nuisance shutdowns of the burner, and due to the normal presence of other and conventional control devices for sensing proper operation of a furnace or a boiler after the burners thereof have been properly ignited.

In Fig. 2 of the drawings there is shown a typical installation of this control system in which the boiler or furnace structure 126 carries the burner mounting or front 121 having therein the usual main burner 122. A fuel supply pipe or conductor 123 leads to the main burner through a pair of fuel shut-off or control valves 124 arranged in series in the usual manner. A small branch conductor 125 leads from the fuel conductor downstream of the valves 124 and is operatively connected to a fuel pressure sensing means 126 which contains the switch 94. The pilot burner 75 and its flame-sensing electrodes may be located in any suitable one of the usual access or inspection openings 127 of the burner front 121, and the photocell 107 may desirably be exposed to the main burner flame through another of said openings. A separate fuel supply 128 is provided for conducting fuel through the solenoid valve 114 to the pilot burner fuel supply line 115. There is also provided in the burner front a conventional air register control 129 for regulating the supply of combustion air to the main burner, the register being supplied in the usual manner with air admitting and excluding means.

For operating the gas valves 124 in unison, any suitable type of actuating or operating means may be employed, it being desirable to utilize a reversible three wire type electric motor 130 driving a variable speed reduction gear 131 which in turn, swings an arm 132 through a limited vertical arc. The outer end of the arm 132 is connected by a vertical actuating link 133 to operating arms 134 provided upon the stems 135 of the valves 124. The arms 134 and 132 may he provided with a plurality of openings in order that the connection points of the link 133 thereto may be varied as necessary .or desirable for proper opening and closing of the valves 124.

In a similar fashion, a reversible three wire type driving motor 136 is provided for operating a variable speed reduction gear 137 which swings an operating .arm 138 through a vertical arc and by means of a vertical link 139 actuates the air register control 129 through an arm '140 attached thereto.

The reduction gears 131 and 137 are provided with driven shafts 141 and 142, respectively, upon which the arms 132 and 138 are mounted and which carry switch operating cams 143. The latter are shown in more detail in Fig. 4, and it will be observed that the cam is adapted to engage and actuate at each end of a limited path of travel the rollers 144 of the operating arms 145 of a pair of limit switches 146. In the usual manner, these limit switches function to halt the operation of the motors 130 and 136 when the fuel valve and air register are either fully open or fully closed. The interlock switches which form a component part of the control 'system are mounted upon the valves 124 and the fair register control 129, and a typical structure of the interlock switches is illustrated in Fig. 3. The subject valve or air register operating stem or shaft 135, carries a cam 147 adapted to engage and actuate the arm 148 of an upper interlock switch unit 149 and the arm 150 of a lower interlock switch unit 151 at each end of its path of travel. For the sake of simplicity and clarity, the switches 92, 93 and 98 have been illustrated in the wiring diagram of Fig. l as single cam operated switches. In the structure illustrated in Fig. 2, however, each of these switches would, in reality, be composed of three switches mounted in series, one upon each of the fuel valves and one upon the register. Since the interlock switches, as illustrated in Fig. 3, may be identical for each of the fuel valves and for the air register, and since the upper switch unit 149 of all three interlock switches will be actuated at the same time with the lower switch units 151 also being actuated at the same time, it is apparent that explanation of operation of one of the interlock switch structures will explain the operation of all of said switches. Assuming that the arms 134 and 140 move downwardly to close the fuel valves and air register, it will be seen that such downward movement, will through the cams 147, swing the switch arms 150 downwardly as viewed in Fig. 3. The switch unit 151 carries the normally-open switch 92 which is closed by the downward movement of the arm 151i, and this switch functions in the circuit of Fig. l as previously explained. When the fuel valves and air register are closed, and the arm 15b is swung downwardly, the switch unit 151 is actuated to close the switch 92 in order to complete the circuit to the coil of the relay 161. It is quite apparent that by suitable cutting or shaping of the cam 147, the opening of the switch 92 may be delayed a second or so after actuation of the cam with the consequent rotation of the cam 147 counter-clockwise as viewed in 'Fig. '3. After this small initial rotation of the cam, however, the arm 150 is allowed to swing upwardly opening the switch 92.

The switch unit 149 desirably carries the normally-open switch 98 and the normally-closed switch 93 which are actuated when the arm 148 is swung upwardly by the cam 147 as the fuel valve and air register reach their fully open position. As is shown schematically in Fig. 7, when the cam comes into engagement with the roller of the arm 148, the normally-closed contacts or switch 93 is opened, and the normally-open contacts or switch 98 is closed.

In Fig. there is shown a front view of the central station control unit which includes a master control knob 152 for operating the switch 5 and moving the same into a fuel valve and air register opening position 153 or closing position 154, as well as the neutral position 155 in which the switch engages the terminal 64. There may also be provided colored lenses 156 through which the signal lamps 105 and 112 may be observed. The unit also carries a knob 157 for operating the switch 63 and adjusting the air register opening, along with suitable and conventionally actuated signal lights 158 indicating the condition of the fuel valve.

In Fig. 6 is shown a front view of the local control station for igniting the pilot burner, this unit being provided with a hand knob 159 for moving the switch 109 into automatic position in engagement with the terminal 72, or manual position in engagement with the terminal 110. The unit further may carry a push button 160 for momentary actuation of the switch 82, as well as a lens 161 through which the signal lamp 73 may be observed.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What we claim and desire to secure by Letters Patent is:

1. A control system for fuel burners having a main burner and a pilot burner including, a main burner fuel valve, a pilot burner fuel valve, a pilot burner ignitor, a first sensing means for detecting the presence of a pilot burner flame and including a normally open circuit closed upon the detecting of the presence of a pilot burner flame, a second sensing means for detecting the presence of a main burner flame and including a normally open circuit closed upon the detecting of the presence of a main burner flame, a third sensing means for detecting the fully-open position of the main burner valve and including a normally open circuit closed upon the detecting of a fully open position of the main burner valve, first electricallyoperated control means for opening the main burner valve, second electrically-operated control means for closing the main burner valve, a firing relay having an energizing coil and normally-open and normally-closed contacts, a closable first energizing circuit to the firing relay coil for energizing the firing relay, a second energizing circuit to the firing relay coil through the normally open circuits of the first and second and third sensing means, time delay means providing a by-pass energizing circuit around the second energizing circuit to the firing relay coil for a predetermined period of time after energization of the system, a valve opening circuit to the first control means through normally-open contacts of the firing relay, a valve closing circuit to the second control means through normallyclosed contacts of the firing relay, and means for opening the first energizing circuit following energization of the firing relay.

2. A control system as set forth in claim 1, wherein the firing relay has normally-open contacts in the second energizing circuit.

3. A control system as set forth in claim 1, wherein the 1. time delay means includes a switch opened by the opening of the main burner fuel valve.

4. A control system as set forth in claim 1, wherein the time delay means includes a switch opened by the delivery of fuel under pressure to the main burner.

5. A control system as set forth in claim 1, and a holding relay having at least two pairs of normally-open contacts and an energizing coil, a primary energizing circuit to the latter coil through normally-open contacts of the firing relay, a secondary energizing circuit to the latter coil through one pair of normally-open contacts of the holding relay, the second pair of normally-open contacts of the holding relay being interposed in the valve closing circuit whereby upon de-energization of the firing relay the valve closing circuit is closed.

6. A control system for fuel burners having a main burner and a pilot burner including, a main burner fuel valve, a first sensing means for detecting the presence of a pilot burner flame and including a normally open circuit closed upon the detecting of the presence of a pilot burner flame, a second sensing means for detecting the pre'sence'of a main burner flame and including a normally open circuit closed upon the detecting of the presence of a main burner flame, a third sensing means for detecting the full open position of the main burner valve and including a normally open circuit closed upon the detecting of a fully open position of the main burner valve, first electrically-operated control means for opening the main burner valve, second electrically-operated control means for closing the main burner valve, a firing relay having an energizing coil and normally open and normally closed contacts, a closable first circuit to the firing relay coil for energizing the firing relay, a second circuit to the firing relay coil through the normally open circuits of the first and second and third sensing means, time delay means for providing a shorting circuit around the second circuit to the firing relay coil for a predetermined period of time after energization of the system, a valve opening circuit to the first control means through normally open contacts of the firing relay, a valve closing circuit to the second control means through normally closed contacts of the firing relay, a holding relay having at least two pairs of normally open contacts and at least one pair of normally closed contacts and an energizing coil, a circuit to the energizing coil of the holding relay through normally open contacts of the firing relay, a circuit to the energizing coil of the holding relay through one pair of normally open contacts of the holding relay, the second pair of normally open contacts of the holding relay being interposed in the valve closing circuit whereby upon de-energization of the firing relay the valve closing circuit is closed, and the normally open contacts of the holding relay being interposed in the first circuit to the firing relay coil whereby upon energization of the holding relay, the first circuit to the firing relay coil is opened and energization of the firing relay is made dependent upon continued closure of the second circuit to the firing relay coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,138,796 Sparrow Nov. 29, 1938 2,243,715 Miller May 17, 1941 2,388,124 Crews Oct. 30, 1945 2,412,990 Kruse Dec. 24, 1946 2,427,178 Aubert Sept. 9, 1947 2,519,889 Crawford Aug. 22, 1950 

